Alcohols of long chain olefins having about 10 to 28 carbon atoms have considerable commercial importance in a variety of applications, including detergents, soaps, surfactants, and freeze point depressants in lubricating oils. These alcohols are produced by a number of commercial processes, such as by oxo or hydroformylation of long chain olefins. Typical commercially available long chain alcohols are the NEODOL® alcohols available from Shell Chemical Company, the EXXAL® alcohols available from Exxon Chemical Company, and the LIAL® alcohols available from Enichem.
In the manufacture of the NEODOL® alcohols, a redominantly linear olefin feed is subjected to hydroformylation by reacting carbon monoxide and hydrogen onto the olefin in the presence of an oxo catalyst to form an alcohol. Over 80% of the alcohol molecules in the resulting alcohol are linear primary alcohols. Of the branched primary alcohols in the composition, most, if not all of the branching is on the C2 carbon atom relative to the hydroxyl bearing carbon atom. These alcohols subsequently can be converted to anionic or nonionic detergents or general surfactants by sulfonation or ethoxylation of the alcohol, or by conversion of the alcohol to an alcohol-ethoxysulfate.
The NEODOL® alcohols are commercially successful intermediates to the production of detergents. One reason for this success undoubtedly is that the NEODOL® alcohols are economically produced with high yields of linear alcohols. The sulfonates of linear alcohols are more biodegradable than the sulfonates of branched long chain alcohols. Since detergents and soaps used by consumers for washing ultimately are released into the environment, the need for surfactants or detergents with maximal biodegradability is well recognized.
The highly linear NEODOL® alcohols have the advantage of a high level of biodegradability; however, the high degree of linearity of these alcohols also increases their hydrophobicity, thereby decreasing their cold water solubility/detergency. Government regulations call for both increased biodegradability and increased solubility.
Alcohols that have been found to meet both the biodegradability and the solubility government standards are branched primary alcohols (and their sulfate derivatives): having about 8 to about 36 carbon atoms; having an average number of branches per molecular chain of at least 0.7 (defined below); having less than 0.5 atom % of quaternary carbon atoms; and, having at least methyl and ethyl branching. These alcohols, as well as a method for preparing them, are described in U.S. Pat. No. 5,849,960, incorporated herein by reference. The method basically involves contacting a feed comprising linear olefins having 7 to 35 carbon atoms with a skeletal isomerization catalyst, and converting the resulting skeletally isomerized olefin to a saturated branched primary alcohol, preferably by hydroformylation.
Unfortunately, olefin feedstreams have been found to contain at least some level of dienes. Dienes can lower the catalytic performance of many commonly used catalysts, such as those used for skeletal isomerization of olefins and those used for hydroformylation.